1. Field of the Invention
The present invention relates to a valve timing control device of an internal combustion engine, that variably controls an open/close timing of engine valves (viz., intake and/or exhaust valves) in accordance with an operation condition of the engine.
2. Description of the Related Art
Hitherto, various valve timing control devices have been proposed and put into practical use particularly in the field of automotive internal combustion engines.
One of them is shown in Japanese Laid-open Patent Application (Tokkai) 2002-357105.
The valve timing control device of the publication generally comprises a vane member that is rotatable about its axis relative to a housing between the most retarded position and the most advanced position. For rotating the vane member in retarding or advancing direction, there are defined between the vane member and the housing retarding and advancing chambers. That is, when the retarding chambers are fed with a hydraulic pressure, the vane member is turned in a retarding direction thereby to retard the open/close operation of engine valves (viz., intake and/or exhaust valves), while when the advancing chambers are fed with the hydraulic pressure, the vane member is turned in an advancing direction thereby to advance the open/close operation of the engine valves.
The valve timing control device further comprises a rotation restricting means that restricts rotation of the vane member from a center position to the most retarded position or the most advanced position in a given condition.
The rotation restricting means comprises retarding and advancing pins that are retractably installed in respective holding bores formed in the vane member, retarding and advancing recesses that are formed in the housing and sized to receive leading ends of the retarding and advancing pins respectively, biasing springs that are respectively installed in the retarding and advancing recesses to bias the pins in a direction to project outward that is toward the retarding and advancing recesses, push back chambers that are respectively defined by the retarding and advancing recesses to push back the pins toward the holding bores against the biasing springs when fed with a hydraulic fluid and a hydraulic pressure control means that controls the pressure of the hydraulic fluid in accordance with an operation condition of the engine.
When the engine is stopped, the push back chambers are suppressed from being fed with the hydraulic fluid and thus, the retarding and advancing pins are projected into the corresponding retarding and advancing recesses due to the force of the biasing springs. With this, the vane member is held or locked at the center position.
While, when, after staring of the engine, the same is brought a predetermined operation condition, both the push back chambers are fed with a hydraulic fluid thereby to disengage the retarding and advancing pins from the corresponding recesses, and the vane member is turned in the retarding or advancing direction in the above-mentioned manner in accordance with the operation condition of the engine.